Device for controlling fuel injection device

ABSTRACT

Provided is a device for controlling a fuel injection device capable of suppressing deterioration of exhaust performance while ensuring driving performance when acceleration of a vehicle is requested during an intake stroke. Therefore, when the acceleration of a vehicle is requested during an intake stroke in one combustion cycle, an engine control unit  9  estimates an increase (acceleration intake air amount Qad) of the amount of air taken in a combustion chamber  19  of an internal combustion engine  1  associated with the acceleration of the vehicle after the acceleration of the vehicle is requested in one combustion cycle based on a lift amount of an intake valve  3 . The engine control unit  9  controls a fuel injection valve  5  so as to increase a fuel injection amount in one combustion cycle according to the acceleration intake air amount Qad.

TECHNICAL FIELD

The present invention relates to a device for controlling a fuelinjection device.

BACKGROUND ART

In a cylinder injection type internal combustion engine capable ofdirectly injecting fuel into a cylinder of an internal combustionengine, it is possible to inject fuel in a wide range from an intakestroke to a compression stroke, and a fuel injection amount of thecylinder injection type internal combustion engine is calculated basedon an intake air amount detected by an air flow meter (AFM: Air FlowMeter) at the start of the intake stroke.

However, if the intake air amount during the intake stroke increases atthe time of acceleration and the like after measurement of the intakeair amount by the air flow meter (AFM), an air-fuel ratio becomes lean,and it is considered that exhaust performance and driving performanceare affected.

As a solution to this problem, it is disclosed that a fuel injectionamount is calculated based on an operation state of an internalcombustion engine, the calculated injection amount of fuel is injectedinto a combustion chamber during an intake stroke, separately from thisfuel injection amount, at the end timing of the intake stroke, theamount of air taken in the combustion chamber of the internal combustionengine is measured, a fuel correction amount is calculated based on themeasured intake air amount, and the calculated correction fuel isadditionally injected into the combustion chamber from the end timing ofthe intake stroke (for example, refer to PTL 1). In this technique,insufficient fuel is additionally injected into the combustion chamberfrom the end timing of the intake stroke.

CITATION LIST Patent Literature

PTL 1: JP 2000-257476 A

SUMMARY OF INVENTION Technical Problem

According to the technique disclosed in PTL 1, the amount of airincreased associated with acceleration or the like during an intakestroke after measurement of an intake air amount is detected until theend timing of the intake stroke, and the shortage of fuel is injectedfrom the end timing of the intake stroke. Therefore, the shortage of thefuel injection amount can be accurately calculated. However, since thecalculation timing of the shortage of the fuel injection amount isdelayed, depending on the calculated fuel injection amount and an enginerotation speed, the fuel is injected during a compression stroke, anddue to fuel adhesion to a piston crown surface and a wall surface of acombustion chamber, exhaust performance may be deteriorated.

Further, in the method in which the fuel injection is performed aplurality of times in one cycle in the intake stroke and the compressionstroke as in multistage injection control, the injection timing of thebasic fuel injection amount is set. Therefore, the shortage of fuelincreased during the intake stroke associated with acceleration and thelike cannot be injected from the end timing of the intake stroke but isinjected during the compression stroke. Therefore, there is apossibility that the exhaust performance further deteriorates.

An object of the present invention is to provide a device forcontrolling a fuel injection device capable of suppressing deteriorationof the exhaust performance while ensuring the driving performance whenacceleration of a vehicle is requested in the intake stroke.

Solution to Problem

To achieve the above-described object, the present invention provides adevice for controlling a fuel injection device, including an estimationunit and a control unit. When acceleration of a vehicle is requestedduring an intake stroke in one combustion cycle, based on a lift amountof an intake valve, the estimation unit estimates an increase in theamount of air taken in a combustion chamber of an internal combustionengine associated with the acceleration of the vehicle after theacceleration of the vehicle is requested in the one combustion cycle.The control unit controls the fuel injection device so as to increase afuel injection amount in the one combustion cycle according to theincrease in the air amount estimated in the estimation unit.

Advantageous Effects of Invention

According to the present invention, when acceleration of a vehicle isrequested in an intake stroke, it is possible to suppress deteriorationof exhaust performance while ensuring driving performance. Issues,configurations, and effects other than the above are clarified bydescriptions of the following embodiments.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a spark ignition internal combustionengine and a control device according to an embodiment of the presentinvention.

FIG. 2 is an internal configuration diagram of a control unit.

FIG. 3 is a chart indicating an intake valve lift amount at the timingof acceleration determination and an integrated air amount during anintake stroke.

FIG. 4 is a chart indicating the relationship between an intake valvelift amount at the time of acceleration determination and an air amountratio during an intake stroke.

FIG. 5 is a time chart indicating a first multistage injection method atthe time of acceleration determination.

FIG. 6 is a time chart indicating a second multistage injection methodat the time of acceleration determination.

FIG. 7 is a flowchart indicating a method of calculating a fuelinjection correction amount at the time of acceleration determination.

FIG. 8 is a flowchart indicating a fuel injection control method of afuel injection correction amount.

FIG. 9 is a flowchart indicating a fuel injection control method of afuel injection correction amount.

FIG. 10 is a time chart indicating a third multistage injection methodat the time of acceleration determination.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the configuration and operation of an engine control unit9, which is a device for controlling a fuel injection device accordingto an embodiment of the present invention, will be described withreference to the drawings.

(Basic Configuration)

FIG. 1 is a basic configuration diagram of an internal combustion engine1 and its control device according to an embodiment of the presentinvention. A cylinder injection type internal combustion engine isexemplified in the following description, but a port injection typeinternal combustion engine and a dual injection type internal combustionengine having both in-cylinder injection and port injection are alsoapplicable.

In FIG. 1, the internal combustion engine 1 is provided with a piston 2,an intake valve 3, and an exhaust valve 4. Intake air passes through anintake air flow meter 18 (AFM), enters a throttle valve 17, and issupplied to a combustion chamber 19 of the internal combustion engine 1from a branch intake manifold 14 via an intake pipe 10 and an intakevalve 3. Fuel is injected and supplied to the combustion chamber 19 ofthe internal combustion engine 1 from a fuel injection valve 5 (fuelinjection device) and ignited by an ignition coil 7 and an ignition plug6. Exhaust gas after combustion is discharged to an exhaust pipe 11 viaan exhaust valve 4, and a three-way catalyst 12 for purifying exhaustgas is provided in the exhaust pipe 11.

A signal from a crank angle sensor 15 of the internal combustion engine1, an air amount signal from the intake air flow meter 18 (AFM), asignal from an air/fuel ratio sensor 13 for detecting an air/fuel ratioin exhaust gas, a signal of an accelerator opening or the like from anaccelerator opening sensor 20 are input to the engine control unit 9.The engine control unit 9 calculates a required torque from theaccelerator opening sensor 20 to the internal combustion engine,determines an idling state, calculates an intake air amount necessaryfor the internal combustion engine 1, and outputs an opening signalcorresponding thereto to the throttle valve 17. A fuel injection signalis output to the fuel injection valve 5, and an ignition signal isoutput to the ignition plug 6.

FIG. 2 illustrates the internal configuration of the engine control unit9.

The engine control unit 9 includes a microcomputer incorporating aninput circuit 101, an A/D conversion unit 102, a central processing unit103, a ROM 104 (Read Only Memory), a RAM 105 (Random Access Memory), andan output circuit 106. When an input signal 100 is an analog signal (forexample, a signal from the intake air flow meter 18 (AFM), theaccelerator opening sensor 20, etc.), the input circuit 101 removes anoise component from the signal and outputs the signal to the A/Dconversion unit 102.

The central processing unit 103 has a function of acquiring an A/Dconversion result and executing a fuel injection control program and theother control program stored in a medium such as the ROM 104 to performeach control and diagnosis. A calculation result and the A/D conversionresult are temporarily stored in the RAM 105, and the calculation resultis output as a control signal 107 through an output circuit 106 and usedfor controlling the fuel injection valve 5, the ignition coil 7, etc.

Comparative Example

Next, an air amount transition during an intake stroke by predeterminedacceleration determination will be described with reference to FIG. 3.In the case of intake stroke injection, in fuel injection control, afuel injection amount is calculated based on an engine speed of aninternal combustion engine and an intake air amount detected by theintake air flow meter 18 (AFM) at the start of an intake stroke.

In the case of multistage injection in which fuel injection is performeda plurality of times during one cycle from the start of an intake stroketo the end of a compression stroke, it is considered that the fuelinjection amount is calculated based on an engine speed of the internalcombustion engine and the intake air amount detected by the intake airflow meter 18 (AFM) at the start of the intake stroke, and the fuelinjection amount is corrected based on the latest information at thestart of the compression stroke.

In this case, the intake air amount which is the basis of the fuelinjection amount calculation is the intake air amount detected by theintake air flow meter 18 (AFM) at the start of the intake stroke and avalue detected before point A at which the intake valve 3 starts toopen. In the case where acceleration is not determined (when it isdetermined that acceleration of a vehicle is not requested), an intakeair amount per unit time is substantially constant, the integratedamount of air taken in a combustion chamber of an internal combustionengine in one cycle has a behavior like the behavior before accelerationof FIG. 3, and the integrated air amount at point C at which the intakevalve 3 closes becomes a pre-acceleration air amount a.

In addition, when acceleration is determined at point B in FIG. 3 (whenit is determined that acceleration of a vehicle is requested), theamount of intake air taken in the combustion chamber of the internalcombustion engine increases after acceleration determination, theintegrated amount of intake air taken in the combustion chamber of theinternal combustion engine during one cycle has a behavior like thebehavior after acceleration of FIG. 3, and the integrated air amount atpoint C at which the intake valve 3 closes becomes a post-accelerationair amount b. At this time, an increase in the intake air amount due tothe acceleration request is a difference between the pre-accelerationair amount a and the post-acceleration air amount b. To accuratelydetect the increase in the air amount due to the acceleration request,it is effective to detect the intake air amount at point C(=post-acceleration air amount b) at which the intake valve 3 closes.

When the amount of intake air at the end of an intake stroke (point C)(=post-acceleration air amount b) is detected, and the fuel injectionamount is calculated from the increase in the air amount (=b−a) due tothe acceleration request, the fuel corresponding to the increase in theair amount can be supplied to the combustion chamber of the internalcombustion engine, and deterioration of the driving performance and thestarting performance due to fuel shortage can be suppressed. However,since the fuel injection start timing is a compression stroke, it isconcerned that exhaust performance is deteriorated due to fuel adhesionto a piston crown surface and a wall surface of the combustion chamberof the internal combustion engine.

(Calculation of Intake Air Amount at the Time of Acceleration)

In FIG. 4, a method of calculating the acceleration intake air amountQad at the time of occurrence of an acceleration request, which is asolution to the problem raised in the comparative example, will bedescribed. The acceleration intake air amount Qad means an increaseamount associated with acceleration of the vehicle, of the amount of airtaken in the combustion chamber of the internal combustion engine afteracceleration of a vehicle is requested in one combustion cycle.

In the present embodiment, in the case of determining the increase in anair amount due to an acceleration request (when it is determined that avehicle acceleration is requested), a fuel injection amount iscalculated based on the amount of intake air taken in the combustionchamber of the internal combustion engine at the end of an intakestroke, and fuel injection during an intake stroke is immediatelycorrected.

In this control, the air amount ratio Qr obtained by integrating a liftamount of the intake valve 3 at predetermined time intervals iscalculated, and the intake air amount is corrected with the calculatedair amount ratio Qr. The air amount ratio Qr is a ratio of the amount ofair taken in the combustion chamber of the internal combustion enginefrom the valve opening start timing (point A) of the intake valve to thevalve closing completion timing (point C) and the amount of air taken inthe combustion chamber of the internal combustion engine from thevehicle acceleration requested timing (point B) to the valve closingcompletion timing (point C). The valve opening start timing is thetiming at which the intake valve 3 starts to open, and the valve closingcompletion timing is the timing at which the intake valve 3 completesvalve closing.

Specifically, the intake air amount which is the basis of the fuelinjection amount calculation is the intake air amount Qstd detected bythe intake air flow meter 18 (AFM) at the start of the intake stroke anda value detected before point A at which the intake valve 3 starts toopen. On the other hand, the air amount ratio Qr is 100% when the intakevalve 3 starts to open at point A and is 0% at the end of vale closingwhich is point C.

In the example of FIG. 4, the air amount ratio Qr corresponds to a ratioof the integrated value (hatched portion in FIG. 4) of the lift amount Lof the intake valve 3 from point B to point C with respect to theintegrated value (time integral value) of the lift amount L of theintake valve 3 from point A to point C.

As illustrated in FIG. 4, when a predetermined acceleration request isgenerated at point B in the figure, and the air amount ratio Qr at thattime is 70%, 70% of total intake air amount during an intake stroke istaken in from point B at which the acceleration request is generated topoint C at which the valve 3 closes. On the other hand, from point A topoint B, about 30% of the total intake air amount during the intakestroke is taken in the combustion chamber of the internal combustionengine.

Therefore, it is possible to calculate the acceleration intake airamount Qad by multiplying the difference between the intake air amountQstd (point A), which is the basis of a fuel injection amountcalculation, and the intake air amount Qacc (point B) at the time ofoccurrence of an acceleration request, by the air amount ratio Qr(correction coefficient). In the present embodiment, the intake airamount Qstd, which is the basis of the fuel injection amountcalculation, is updated at point A to improve the accuracy of theacceleration intake air amount Qad.

As a result, since the intake air amount (acceleration intake air amountQad) which is increased due to the acceleration request at the end ofthe intake stroke is calculated at the time of occurrence of theacceleration request, a fuel corresponding to the increase in the airamount Qad can be supplied in the combustion chamber of the internalcombustion engine during the intake stroke to suppress deterioration ofdriving performance and starting performance due to fuel shortage andalso prevent deterioration of exhaust performance by compression strokeinjection.

Although the idea is the same even when a variable valve mechanism isused for the intake valve 3 and the exhaust valve 4, when valve overlapoccurs in which a valve closing timing of the exhaust valve 4 and avalve opening timing of the intake valve 3 overlap, the intake air isblown through the exhaust pipe 11 due to overlap, and therefore it isnecessary to calculate the intake air amount in consideration of theamount of air blown out.

In addition, in this control, the control method of multistage injectionis also changed to achieve both suppression of deterioration of drivingperformance and starting performance at the time of occurrence of anacceleration request and prevention of exhaust performance deteriorationdue to compression stroke injection.

(Multistage injection control) With respect to a method of changingmultistage injection, the contents of change will be described withreference to the time charts of FIGS. 5 and 6. FIG. 5 assumes multistageinjection control in which fuel injection is performed twice during anintake stroke and once during a compression stroke and indicates thecase where acceleration is determined after the first fuel injection inthe intake stroke.

When acceleration is determined by driver's accelerator operation, asdescribed above, the acceleration intake air amount Qad is calculated bymultiplying the difference between the intake air amount Qstd which isthe basis of the fuel injection amount calculation and the intake airamount Qacc at the time of occurrence of the acceleration request by theair amount ratio Qr (correction coefficient). The fuel injectioncorrection amount Tacc corresponding to the acceleration intake airamount Qad can be calculated from an engine speed and the accelerationintake air amount Qad, but it may be calculated using a map or the likestored in a storage medium.

When the correction amount Tacc calculated here is injected immediatelyafter fuel injection (injection pulse width Ti3) during an compressionstroke or injected combined with the fuel injection (injection pulsewidth Ti3) during the compression stroke, the injection period duringthe compression stroke is extended, and it is concerned that exhaustperformance is deteriorated due to fuel adhesion to a piston crownsurface or a combustion chamber wall surface of the internal combustionengine.

As a countermeasure, to prevent the fuel injection during thecompression stroke when acceleration is determined, it is controlledsuch that, at the ignition start timing of the second fuel injection(injection pulse width Ti2) during the intake stroke after accelerationdetermination, the second fuel injection (injection pulse width Ti2)during the intake stroke and remaining fuel injection (injection pulsewidth Ti3) during the compression stroke are performed at once by addingthe fuel injection correction amount Tacc corresponding to the increasein the intake air amount Qad due to the acceleration determination.Accordingly, it is possible to supply the fuel corresponding to theamount of intake air taken in the combustion chamber of the internalcombustion engine during one cycle without excess or deficiency suchthat it is possible to ensure the driving performance and also suppressdeterioration of the exhaust performance.

In addition, FIG. 6 assumes multistage injection control in which fuelinjection is performed twice during the intake stroke and once duringthe compression stroke and indicates the case where acceleration isdetermined before the first fuel injection during the intake stroke.

When acceleration is determined by driver's accelerator operation, thefuel injection correction amount Tacc corresponding to the increase inthe intake air amount Qad due to acceleration determination iscalculated similarly to the above case.

In the example of FIG. 6, to prevent the fuel injection (injection pulsewidth Ti3) during the compression stroke when acceleration isdetermined, it is controlled such that, immediately after theacceleration determination, the first fuel injection (injection pulsewidth Ti1) during the intake stroke, the second fuel injection(injection pulse width Ti2) during the intake stroke, and remaining fuelinjection (injection pulse width Ti3) during the compression stroke areperformed at once by adding the fuel injection correction amount Tacccorresponding to the increase in the intake air amount Qad due to theacceleration determination. In this case also, it is possible to supplythe fuel corresponding to the amount of intake air taken in thecombustion chamber of the internal combustion engine during one cyclewithout excess or deficiency such that it is possible to ensure thedriving performance and also suppress deterioration of the exhaustperformance.

(Process flow) Next, a fuel injection control method at the time ofacceleration determination will be described with reference toflowcharts of FIGS. 7, 8, and 9. The flowchart of FIG. 7 indicates therelationship between the calculation of the fuel injection amount andthe fuel injection correction amount calculated at the time ofacceleration determination. Each process of the flowchart is executed bythe engine control unit 9.

When this routine is started, the intake air amount Qstd serving as areference for calculating the fuel injection amount in step S101 isdetected from the output of the intake air flow meter 18 (AFM).

Thereafter, in step S102, it is determined whether it is a timing forcalculating the fuel injection amount.

If it is determined to be a timing for calculating the fuel injectionamount in step S102 (step S102: YES), the process proceeds to step S103,in which the fuel injection amount is calculated based on the currentengine speed and the intake air amount Qstd detected in step S101, andfinishes.

On the other hand, if it is determined not to be a timing forcalculating a fuel injection amount in step S102 (step S102: NO), it isdetermined in step S104 whether a predetermined accelerationdetermination is established. If it is determined in step S104 that apredetermined acceleration determination is established (step S104:YES), in step S105, the intake air amount Qacc at the time when theacceleration determination is established is detected from the output ofthe intake air flow meter 18 (AFM).

Thereafter, in step S106, the intake air amount ratio Qr is calculatedbased on the lift amount of the intake valve assuming that the valveopening start time of the intake valve 3 is 100%, and the valve closingend time is 0%. Here, the engine control unit 9 functions as acalculation unit that calculates the intake air amount ratio Qr based onthe lift amount of the intake valve and stores the intake air amountratio Qr in the RAM 105 (storage unit). Specifically, the engine controlunit 9 (calculation unit) calculates the intake air amount ratio Qrbased on the integrated value of the lift amount of the intake valve.

In the following step S107, from the intake air amount Qacc at the timeof acceleration determination detected in step S105 and the intake airamount ratio Qr (temporarily stored in the RAM 105) calculated in stepS106, the acceleration intake air amount Qad is calculated using thefollowing equation (1). It should be noted that the previouslycalculated intake air amount ratio Qr may be stored in a storage medium,and the acceleration intake air amount Qad may be calculated using thevalue.Qad=(Qacc−Qstd)×Qr  [Mathematical Formula 1]

Here, when acceleration of a vehicle is requested during the intakestroke in one combustion cycle, the engine control unit 9 functions asan estimation unit that estimates an increase (acceleration intake airamount Qad) in the amount of air taken in the combustion chamber of theinternal combustion engine associated with acceleration of a vehicleafter the acceleration of the vehicle is requested in the one combustioncycle based on the lift amount of the intake valve. Thus, before theclosing completion timing of the intake valve 3, the increase in theamount of air taken in the combustion chamber of the internal combustionengine associated with acceleration of a vehicle can be calculated afteracceleration of a vehicle is requested in one combustion cycle.

Thereafter, in step S108, the fuel injection correction amount Tacc iscalculated based on the acceleration intake air amount Qad and theengine speed, calculated in step S107. The engine control unit 9functions as a control unit that controls the fuel injection device soas to increase the fuel injection amount in one combustion cycleaccording to the acceleration intake air amount Qad.

The injection method of the fuel injection correction amount Tacccalculated in step S108 will be described in detail with reference tothe flowcharts of FIGS. 8 and 9. On the other hand, if it is determinedin step S104 that the predetermined acceleration determination is notestablished (step S104: NO), no processing is performed, and the processfinishes.

FIGS. 8 and 9 are flow charts indicating the fuel injection controlmethod of the fuel injection correction amount Tacc calculated in stepS108, and the method starts from A in FIG. 8. In this flowchart, thecase of multistage injection control in which fuel injection isperformed twice during an intake stroke and once during a compressionstroke will be exemplified, but setting of the number of injectiontimes, the injection timing, and the like is not limited to theembodiment.

First, in step S201, it is determined whether the calculation timing ofthe fuel injection correction amount Tacc calculated in step S108 isbefore the first injection in the intake stroke. If it is determined instep S201 that the calculation timing is before the first injectionduring the intake stroke (step S201: YES), the process proceeds to stepS202, in which the set multistage injection control is canceled, all ofthe fuel injection amounts set during one cycle are added, and the addedinjection amount Ti is calculated, as expressed by the followingequation (2). Ti, Ti1 to Ti3 correspond to an injection pulse widthindicating a period during which fuel is injected from the fuelinjection valve 5.Ti=Ti1+Ti2+Ti3  [Mathematical Formula 2]

Thereafter, in step S203, the fuel injection correction amount Tacccalculated in step S108 is added to the added injection amount Ticalculated in step S202 as expressed by the following equation (3), tocalculate the acceleration fuel correction amount Te.Te=Ti+Tacc  [Mathematical Formula 3]

In the following step S204, fuel injection is immediately executed basedon the acceleration fuel correction amount Te obtained in step S203, andthe process is finished. On the other hand, if it is determined in stepS201 that the calculation timing of the fuel injection correction amountTacc is not before the first injection during the intake stroke (stepS201: NO), the process proceeds to step S205, and it is determinedwhether the calculation timing of the fuel injection correction amountTacc calculated in step S108 is before the second injection during theintake stroke. If it is determined in step S205 that the calculationtiming is before the second injection in the intake stroke (step S205:YES), the process proceeds to step S206, in which the set multistageinjection control is canceled, all of the remaining fuel injectionamounts set during one cycle are added, and the added injection amountTi is calculated, as expressed by the following equation (4).Ti=Ti2+Ti3  [Mathematical Formula 4]

In other words, the engine control unit 9 (control unit) performs firstcontrol to cause the fuel injection valve 5 (fuel injection device) toperform fuel injection for a set number of times in one combustion cycleaccording to an operation state of the internal combustion engine (anengine speed, the temperature of a cooling water, the temperature of anengine oil). If acceleration of a vehicle is requested in an intakestroke during the first control, the engine control unit 9 cancels thefirst control and performs the second control to cause the fuelinjection valve 5 to perform fuel injection once after the vehicleacceleration is requested in one combustion cycle.

Thereafter, in step S207, by adding the fuel injection correction amountTacc calculated in step S108 to the added injection amount Ti calculatedin step S206 as expressed by the following equation (3), theacceleration fuel correction amount Te is calculated. In the followingstep S208, fuel injection is immediately executed based on theacceleration fuel correction amount Te obtained in step S207, and theprocess is finished. On the other hand, if it is determined in step S205that the calculation timing of the fuel injection correction amount Taccis not before the second injection in the intake stroke (step S205: NO),the process proceeds to B and moves to the flowchart of FIG. 9.

FIG. 9 is a flowchart when the calculation timing of the fuel injectioncorrection amount Tacc is determined not to be before the secondinjection during the intake stroke in step S205, and the flowchartstarts from B of FIG. 9.

First, in step S301, it is determined whether the calculation timing ofthe fuel injection correction amount Tacc calculated in step S108 isbefore the first injection in the compression stroke. If it isdetermined in step S301 that the calculation timing is before the firstinjection in the compression stroke (step S301: YES), the processproceeds to step S302 to determine whether fuel injection can be startedduring the intake stroke.

For example, the engine control unit 9 may determine that fuel injectioncan be started during the intake stroke when the determination timing instep S302 is a predetermined time before the valve closing completiontiming.

If it is determined in step S302 that fuel injection can be startedduring the intake stroke (step S302: YES), the process proceeds to stepS303 to calculate the acceleration fuel correction amount Te by addingthe fuel injection correction amount Tacc calculated in step S108 to thefuel injection amount Ti3 in the first injection in the compressionstroke as expressed by the following equation (5).Te=Ti3+Tacc  [Mathematical Formula 5]

In the following step S304, the fuel injection is immediately performedbased on the acceleration fuel correction amount Te obtained in stepS303, and the process is finished. On the other hand, if it isdetermined in step S301 that the calculation timing of the fuelinjection correction amount Tacc is not before the first injection inthe compression stroke (step S301: NO), the process proceeds to stepS305 to determine to perform correction in the intake stroke injectionof the next cylinder without performing acceleration fuel correctionduring the compression stroke, and the process is finished.

In other words, the internal combustion engine 1 has at least a firstcylinder and a second cylinder to be ignited next to the first cylinder,and the engine control unit 9 (control section) determines whether ornot the last fuel injection in one combustion cycle can be startedduring an intake stroke for the first cylinder. If the last fuelinjection in one combustion cycle cannot be started during the intakestroke for the first cylinder, the fuel injection valve 5 (fuelinjection device) is controlled so as to increase the fuel injectionperiod of the last fuel injection in one combustion cycle for the secondcylinder in accordance with the acceleration intake air amount Qadestimated for the first cylinder.

Even when it is determined in step S302 that fuel injection cannot bestarted during the intake stroke (step S302: NO), the process proceedsto step S305, in which it is determined to perform acceleration fuelcorrection in the intake stroke injection for the next cylinder withoutperforming the correction during the compression stroke, and the processis finished.

As described above, according to the present embodiment, whenacceleration of a vehicle is requested during an intake stroke, it ispossible to suppress deterioration of exhaust performance while ensuringdriving performance

That is, in the configuration of the present embodiment, when apredetermined acceleration request occurs, according to the intake airamount before the acceleration request, the intake air amount at thetime of occurrence of the acceleration request, and valve operation ofthe intake valve, an acceleration intake air amount is calculated whichincreases during one combustion cycle in association with theacceleration request, and a fuel injection amount can be immediatelycorrected based on the acceleration intake air amount. Therefore, fuelshortage due to the increase in the intake air amount during an intakestroke can be solved, and driving performance such as starting andaccelerating can be improved.

In addition, since the fuel injection amount is corrected immediatelyupon occurrence of the acceleration request, fuel injection within theintake stroke becomes possible, fuel injection is not performed in thecompression stroke, fuel adhesion to a piston wall surface and acombustion chamber wall surface is avoided, and deterioration of exhaustperformance can be suppressed.

(Variation)

FIG. 10 is a diagram indicating an example of multistage injection inwhich fuel injection is performed three times in the intake stroke. Theengine control unit (control unit) executes control to cause the fuelinjection valve 5 (fuel injection device) to perform fuel injectionthree times (set number of times) in one combustion cycle according tothe operating state of the internal combustion engine.

When acceleration of a vehicle is requested during an intake stroke ofone combustion cycle, the engine control unit 9 controls the fuelinjection valve 5 (fuel injection device) so as to increase a fuelinjection period of the last fuel injection in one combustion cycleaccording to the acceleration intake air amount Qad.

In the present variation, since the multistage injection is performedonly in the intake stroke, it is not necessary to cancel multistageinjection control and perform control in which the fuel injection valve5 performs fuel injection once after the acceleration of a vehicle isrequested in one duel combustion cycle. Thereby, it is possible toobtain the effect of multistage injection (for example, suppression ofparticulate matter).

In the present variation, the engine control unit 9 (control unit)increases the fuel injection period of the last fuel injection in onecombustion cycle according to the acceleration intake air amount Qad,but a predetermined injection interval can be secured, and if the fuelinjection is in time, the fuel injection period of either the first orthe second fuel injection may be increased.

Further, the engine control unit 9 determines whether or not the lastfuel injection in one combustion cycle can be started during the intakestroke for the first cylinder (cylinder corresponding to #1 in FIG. 10),and when the last fuel injection in the one combustion cycle cannot bestarted during the intake stroke for the first cylinder, according tothe acceleration intake air amount Qad estimated for the first cylinder,the fuel injection valve (fuel injection device) may be controlled so asto increase the fuel injection period in one combustion cycle for thesecond cylinder (cylinder corresponding to #3 in FIG. 10).

The present invention is not limited to the above-described embodimentsand includes various variations. For example, the above-describedembodiments describe the present invention in detail for clarification,and every configuration described above may not be necessarily included.Further, a configuration of each embodiment can be partially replaced toa configuration of the other embodiment. Furthermore, a configuration ofeach embodiment can be added to the configuration of the otherembodiment. Further, a part of a configuration of each embodiment can beadded to, deleted from, and replaced from the other configuration.

Further, each of the above-described configurations, functions, and thelike may be realized by hardware, for example, by designing a part of orall of them by using an integrated circuit. Further, each of theconfigurations and the functions may be realized by software by aprocessor interpreting and performing a program for realizing eachfunction. Information such as a program, a table, and a file forrealizing each function can be stored in a recording device such as amemory, a hard disc, and a solid state drive (SSD) or a recording mediumsuch as an IC card, an SD card, and DVD.

The embodiments of the present invention may be in the followingaspects.

(1) In a device for controlling a fuel injection device which directlyperforms fuel injection for a cylinder of an internal combustion engine,a control unit is provided which controls the fuel injection device soas to perform fuel injection for a set number of times in one cycle.When it is determined to accelerate during an intake stroke in the onecycle, the control unit controls so as to increase the injection widthof subsequent fuel injection based on the amount of intake air duringthe intake stroke.

(2) In a device for controlling a fuel injection device which directlyperforms fuel injection for a cylinder of an internal combustion engine,a control unit is provided which controls the fuel injection device soas to perform fuel injection for a set number of times in one cycle.When it is determined to accelerate during an intake stroke in the onecycle, the control unit controls so as to increase the injection widthof subsequent fuel injection according to operation of an intake valvethat opens and closes an intake side flow path of the internalcombustion engine at that time.

(3) In the device for controlling the fuel injection device according to(1), when it is determined to accelerate during the intake stroke in theone cycle, the control unit controls so as to increase the injectionwidth of the last fuel injection in the one cycle based on the amount ofintake air during the intake stroke.

(4) In the device for controlling the fuel injection device according to(2), when it is determined to accelerate during the intake stroke in theone cycle, the control unit controls so as to increase the injectionwidth of the last fuel injection in the one cycle according to operationof the intake valve that opens and closes the intake side flow path ofthe internal combustion engine at that time

(5) In the device for controlling the fuel injection device according to(1), when it is determined to accelerate during the intake stroke in theone cycle, the control unit controls such that the injection width ofthe last fuel injection during the intake stroke is increased in a rangebefore starting a compression stroke subsequent to the intake stroke,based on the amount of intake air during the intake stroke.

(6) In the device for controlling the fuel injection device according to(2), when it is determined to accelerate during the intake stroke in theone cycle, the control unit controls such that the injection width ofthe last fuel injection during the intake stroke is increased in a rangebefore starting a compression stroke subsequent to the intake stroke,according to operation of the intake valve that opens and closes theintake side flow path of the internal combustion engine at that time.

(7) In the device for controlling the fuel injection device according to(2), when the amount of air taken in the internal combustion engine isthe same in the case where the acceleration is determined, the controlunit controls such that the injection width of the last fuel injectionduring the intake stroke is increased in a range before starting acompression stroke subsequent to the intake stroke according to theoperation of the intake valve that opens and closes the intake side flowpath of the internal combustion engine at that time.

(8) In the device for controlling the fuel injection device according to(1), when the operation of the intake valve that opens and closes theintake side flow path of the internal combustion engine is the same inthe case where the acceleration is determined, the control unit controlssuch that the injection width of the last fuel injection during theintake stroke is increased in a range before starting a compressionstroke subsequent to the intake stroke as the amount of air taken in theinternal combustion engine at that time increases.

(9) In the device for controlling the fuel injection device according to(1) or (2), when the amount of air taken in the internal combustionengine is the same, and the operation of the intake valve that opens andcloses the intake side flow path of the internal combustion engine isthe same in the case where the acceleration is determined, the controlunit controls such that the injection width of the last fuel injectionduring the intake stroke is increased in a range before starting acompression stroke subsequent to the intake stroke as the accelerationdetermination timing becomes early in the intake stroke.

(10) In the device for controlling the fuel injection device accordingto (1) or (2), when the acceleration is determined, the control unitcontrols the injection width of the last fuel injection in the intakestroke based on the amount of air taken in the internal combustionengine at the acceleration determination and the total intake air amountto the internal combustion engine during the intake stroke that isrequired from the operation of the intake valve that opens and closesthe intake side flow path of the internal combustion engine.

(11) In a device for controlling a fuel injection device for directlyperforming fuel injection for a cylinder of an internal combustionengine, a control unit is provided which controls the fuel injectiondevice so as to perform fuel injection for a set number of times in onecycle. The control unit controls the fuel injection device such that afuel injection amount becomes larger than the total fuel injectionamount in the case of performing fuel injection for a set number oftimes. When the control unit controls the fuel injection device so as toperform fuel injection for the set number of times in a first cycle andwhen acceleration is determined in a second cycle subsequent to thefirst cycle, by performing subsequent fuel injection in the second cycleat a long injection pulse with respect to fuel injection of the sametiming in the first cycle, the control unit controls such that the totalfuel injection amount in the second cycle becomes larger than the totalfuel injection amount in the first cycle.

(12) In the device for controlling the fuel injection device accordingto (11), the control unit controls such that the fuel injection isperformed in the second cycle in the number of times smaller than theset number of times in the first cycle when acceleration is determinedin the second cycle.

(13) In the device for controlling the fuel injection device accordingto (11), the control unit sends the long injection pulse to the fuelinjection device so as to be within the intake stroke of the secondcycle.

(14) In the device for controlling the fuel injection device accordingto (11), the control unit controls such that the length of the longinjection pulse is shortened when the acceleration is determined in thelater injection than the first stage of the second cycle in comparisonwith the case where the acceleration is determined in the injection inthe first stage of the second cycle.

According to the above embodiments (1) to (14), at the time ofmultistage injection control, the air amount that increases during theintake stroke associated with acceleration or the like is accuratelycalculated, and the fuel injection amount is calculated based on thecalculated intake air amount. As a result, it is possible to ensure thedriving performance and also suppress deterioration of the exhaustperformance.

REFERENCE SIGNS LIST

-   1 internal combustion engine-   2 piston-   3 intake valve-   4 exhaust valve-   5 fuel injection valve-   6 ignition plug-   7 ignition coil-   8 knock sensor-   9 ECU (engine control unit)-   10 intake pipe-   11 exhaust pipe-   12 three-way catalyst-   13 air fuel ratio sensor-   14 intake manifold-   15 crank angle sensor-   16 signal plate-   17 throttle valve-   18 intake air flow meter (AFM)-   19 combustion chamber-   20 accelerator opening sensor

The invention claimed is:
 1. A device for controlling a fuel injectiondevice, comprising: an estimation unit configured to estimate, whenacceleration of a vehicle is requested during an intake stroke in onecombustion cycle, based on a lift amount of an intake valve, an increasein the amount of air taken in a combustion chamber of an internalcombustion engine associated with the acceleration of the vehicle afterthe acceleration of the vehicle is requested in the one combustioncycle; a control unit configured to control the fuel injection device soas to increase a fuel injection amount in the one combustion cycleaccording to the increase in the air amount estimated in the estimationunit; and a storage unit configured to store an air amount ratioindicating a ratio of the amount of air taken in the combustion chamberof the internal combustion engine from a timing at which theacceleration of the vehicle is requested to a valve closing completiontiming of the intake valve with respect to the amount of air taken inthe combustion chamber of the internal combustion engine from a valveopening start timing of the intake valve to the valve closing completiontiming, wherein the estimate unit estimates an increase in the amount ofair taken in the combustion chamber of the internal combustion engineassociated with the acceleration of the vehicle after the accelerationof the vehicle is requested, based on a difference between an intake airamount measured at a timing before the valve opening start timing and anintake air amount measured at a timing at which the acceleration of thevehicle is requested, and the air amount ratio.
 2. The device forcontrolling the fuel injection device according to claim 1, comprising:a calculation unit configured to calculate the air amount ratio based ona lift amount of the intake valve and stores the air amount ratio in thestorage unit.
 3. The device for controlling the fuel injection deviceaccording to claim 2, wherein the calculation unit calculates the airamount ratio based on an integrated value of the lift amount of theintake valve.
 4. The device for controlling the fuel injection deviceaccording to claim 1, wherein the control unit performs a first controlto cause the fuel injection device to perform fuel injection for a setnumber of times in one combustion cycle according to an operating stateof the internal combustion engine, and the control unit cancels thefirst control when acceleration of a vehicle is requested in an intakestroke during the first control and performs a second control to causethe fuel injection device to perform fuel injection once after theacceleration of the vehicle is requested in the one combustion cycle. 5.The device for controlling the fuel injection device according to claim1, wherein the control unit performs control to cause the fuel injectiondevice to perform fuel injection for a set number of times in onecombustion cycle according to an operating state of the internalcombustion engine, and the control unit controls the fuel injectiondevice so as to increase a fuel injection period of any one of the onecombustion cycles according to an increase in the air amount estimatedin the estimation unit.
 6. The device for controlling the fuel injectiondevice according to claim 5, wherein the control unit controls the fuelinjection device so as to increase the fuel injection period of the lastfuel injection in the one combustion cycle according to the increase inthe air amount estimated in the estimation unit.
 7. The device forcontrolling the fuel injection device according to claim 6, wherein theinternal combustion engine at least includes a first cylinder and asecond cylinder to be ignited next to the first cylinder, the controlunit determines whether or not the last fuel injection in one combustioncycle can be started during an intake stroke for the first cylinder, andwhen the last fuel injection of the one combustion cycle cannot bestarted during the intake stroke for the first cylinder, the controlunit controls the fuel injection device so as to increase a fuelinjection period in the one combustion cycle for the second cylinder,according to an increase in the air amount for the first cylinderestimated by the estimation unit.